Cathode ray tube using replaceable cathode



M. HERTZ CATHODE RAY TUBE USING REPLACEABLE CATHODE July so, 1963 Filed Jan. 15, 1962 [vol \ESaQ s3 was United States Patent 3,099,762 CATHODE RAY TUBE USING REPLACEABLE CATHODE Michael Hertz, 6726 14th Place NW., Washington 12, D.C. Filed Jan. 15, 1962, Ser. No. 166,162 5 Claims. (Cl. 313-74) This invention relates to cathode ray tubes and in particular to the provision of a two-part readily-separable cathode ray tube with the electron source in one part and control electrodes, accelerating electrode, and target for the electrons in another part.

During use of a cathode ray tube very few failures occur in the control and accelerating electrode assembly of the tube or in the target within the tube such as a photophorescent screen, read out conductors or ladders in the face of the screen. The major cause of failure of the tube is due to failure of the electron source as by exhauston of emissive material, flaking off of the same from the supporting cathode metal base, or failure of the cathode heater as by rupture thereof or shorting with the cathode metal base. In addition, emissive material flaked off from its support may short against the control electrode, which in conventional cathode ray tube structure is exceedingly close to the emissive material on the cathode metal base.

The most expensive portion of a cathode ray tube, particularly in the case of color picture tubes, is the glass envelope with the target material on the face of the tube, and in the case of color picture tubes, the mask and associated triple phosphor. Since these parts in most cases can be reused, as is, after cathode supply failure, it is desirable to provide a structure whereby only the electron supply source and so much as is necessary to feed it to the control grid and anode assembly of the cathode ray tube can be readily separated from the remainder of the tube and yet require no further processing of said remainder.

At the present time in order to repair a cathode ray tube which has had cathode emission failure, it is necessary to break the vacuum seal in the cathode ray tube, cut oif the neck portion which contains the electron gun, and replace the gun and neck portion by another. Sometimes, because the cathode ray tube has been unsealed, the phosphor screen is washed off and a new one placed therein, but in most cases such treatment is not necessary and would not be done except for the fact that the tube was unsealed in order to apply the new gun.

It is an object of this invention to provide a tube structure which will enable repair of a cathode ray tube to be effected without breaking the vacuum seal to the portion of the envelope containing the target screen.

It is a further object of the invention to provide a cathode ray structure which will enable the repair of a cathode ray tube without disturbing major portions of its structure.

Other objects of the invention will become apparent upon consideration of the following specification and claims, when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a fragmentary sectional view of a portion of a cathode ray display device embodying the invention,

.together with a tube forming part of the device but shown detached from the remaining portion;

FIG. 2 is a plan view of a socket utilized with the cathode ray display device, and

FIG. 3 is an elevational View of the socket.

Although the invention has been illustrated as embodied in a cathode ray picture tube, it will become obvious that the invention is applicable to other forms of cathode ray tubes.

Now referring to the drawings in greater detail, at 10 is indicated generically an evacuated envelope having a flared portion 12, a neck 14, a face plate 16, and a bottom 18. The face plate carries the target for electrons directed toward it. In this instance the face plate is disclosed as having a phosphorescent coating 20 thereon, as is conventional in the art, though conductive pins or other targets are within the purview of the invention. The envelope on its inner face carries the conventional Aquad-ag coating 22 connected to the high voltage button 24. The bottom of the envelope has an electron permeable window 26 centrally thereof and immediately above the window is a control grid 28, focus and beam forming grids 30 and 32, as is conventional in the art, and an accelerating anode 34. Except for the control grid, the structure of the electrodes in the envelope forms no part of the invention and may be varied, as desired.

If the cathode ray be deflected electromagnetically, the conventional electromagnetic deflecting coils would be placed about the neck of the tube. If the ray be deflected electrostatically, the gun would be furnished with the conventional electrostatic deflecting plates.

The window 26 is a very thin foil of aluminum or the like of a thickness of the order of .001 inch or of electron permeable ceramic material as described in the patent to Seehof et al., No. 2,990,493. The window is fused or brazed to a supporting metal or ceramic ring 36 in turn fused into the bottom of the envelope. For protection of the window against physical damage, it is located within a recess 38 of the bottom and the ring 36 extends slightly thereinto. Extending transversely through the bottom are the leads 40.

Resting on the bottom of the envelope is a spacing ring 42, the ring being positioned between glass nibs 44 which extend from the bottom and through which the leads 40 extend.

The control grid 28 is held in position within the envelope :by means of suitable tabs 46. Pins 48 are secured to the other electrodes in the envelope and these pins are fastened to spacers in the form of ceramic rods 50. The tabs 46 are fastened to adjacent pins 48.

The control grid and other assembled parts are supported from the bottom and so that the grid 28 is seated on the spacer ring which in turn is seated on the bottom of the envelope. Rigid electrical connections are then made between the electrodes within the envelope and the leads traversing the bottom. The control grid may have a hollow extension 52 projecting down to and within the ring 36 as close to the Window 26 as may be desired, the spacing being determined by the length of the extension and thickness of spacing ring. The opening in the control grid and its hollow tube is much smaller than the window so as to facilitate registration of window and opening I while the window is made as of small area as possible to avoid damage thereto and ruptures due to the pressure differential imposed thereon. If desired a coarse metallic netting, not shown, may back the material of window 26 and be interposed between the window material and the supporting ring 36. Since the bottom of the envelope is specially formed, evacuation of the envelope may be eifected through a wall of the neck, the nodule 54 being the remnant tipped oifportion of the exhaust tabulation through which the envelope had been evacuated.

To the lower end of the envelope is detachably mounted an evacuated hermetically sealed cathode tube generically indicated as 60. The tube comprises an insulating cylinder of glass 62 or the like with a bottom 64, initially provided with an exhaust tubulation but in the finished product with a tipoff 66. The cylinder at its upper end is provided with a cylindrical neck 68 capped off with an electron permeable window 70 of the character of the window 26 and extending from the neck slightly, through the intermediary of ring 72. When the tube 60 is thrust up toward the bottom 18 of the envelope, the neck 68 will enter the recess 38 since the neck is made slightly smaller in diameter than the diameter of the recess, and the windows 26 and 70 will come into registration and preferably in intimate contact with one another, the seats on the rings 36 and 72 being both parallel to each other and perpendicular to the longitudinal axis of the envelope and tube. To maintain the tube and envelope in this relationship any conventional means may be employed. Thus, the neck may be provided with screw threads threading into a threaded portion in the base of the tube (not shown). Or a metallic band 74 is clamped about the envelope and a second undercut band 76 is clamped about the tube 60. A number of equally spaced spring hooks 78 are pivotally mounted as at 80 to the band 74. After the tube 60 is positioned with the windows in proper position, the spring hooks are stretched, and hooked beneath the clamp band 76.

Within the tube 60, close to its bottom 64 is a metallic cathode sleeve 82 surmounted by emissive material 84 and containing a heater 86. The heater and cathode sleeve are connected to supporting leads 88 extending through the base 64. The cathode lead is adapted to be connected to ground or the negative side of a high voltage supply and the heater leads to a low voltage supply. Adjacent the window 70 and remote from the cathode is an anode 89 adapted to be connected to the positive end of the high voltage source and to accelerate electrons emitted from the cathode so that they will pass through the windows 70 and 26 and into the envelope. The grid is of wire mesh, 200 to 500 meshes to the inch and preferably of the coarser mesh, and is connected via a rigid lead 90 to an anode cap 91 on the side of the tube. The high voltage button 24 of the envelope and the anode cap 91 may be connected together and to the high voltage source by a harness 92, or if preferred, separate values of high voltage may be applied to the two anode terminals with a common negative connection to the cathode. Usually about 22 kv. is applied to a monochrome so called 2 3 picture tube with higher voltages to color picture tubes. A voltage preferably higher than 22 kv. and of about 25 kv. is applied to the anode 89 to cause penetration of the electrons via the windows into the picture tube envelope.

Electrical connections may be made to the leads 40 :and 88 by making the leads 40 long and utilizing a socket 93 with a thick stepped portion 94 provided with socket pins 95 to engage the leads 40, there being suitable wires 96 connected to the socket pins. The lower step portion 98 of the socket has similar socket pins 100, and leads 102 are connected to the base pins which are connected with leads 88 from the tube 60. An opening 104 is provided in the socket to accommodate the tipoif 66. Should the high voltage lead from accelerating anode 89 be fed through the base, the pins 100 would be all grouped closely together toward an end of the low step portion 98,

and the high voltage lead would be at an isolated area at the other end thereof.

In a three gun color picture tube, three cathode tubes 60 would be utilized with appropriate positioning in associated control grids within the large envelope.

Obviously, with the arrangement described, the removal of a picture tube or the like from its association with a chassis or cabinet and transfer to a factory for reprocessing is, in many instances, avoided, it being merely necessary to remove the socket 93 and connection to the terminal 91, release the spring hooks 78 and to substitute a good tube for the defective tube 60. Then by reapplying the spring hooks, high voltage connections, and socket 93, the cathode ray tube is again ready for use.

If desired, a decelerating grid may be positioned in the envelope 10 between the window 26 and control grid 28 to facilitate control of the grid on the electron stream. Thus, if there be excessive potential on the accelerating anode 89 within the tube 60, the electron stream may be cut down by negative potential applied to the inserted decelerating grid so that the control grid may modulate the electron stream with a low bias potential. The bias potential and decelerating grid potential may be varied inversely simultaneously by potentiometer means under control of a single finger control.

Having thus described the invention, what is claimed 1. In a cathode nay tube, an evacuated envelope having "an electron permeable window, a contnol gi d within the envelope in the path of movement of electnons entering the envelope through the window, beam forming, focusing and electron accelerating electrodes within the envelope, a target supported by the envelope against which the electrons impinge, a coope'nating evacuated tube having an electron permeable window and means therein for generating an electron beam and propelling the same though the window, and means detachably coupling the tube to the envelope with the windows in registration with each other.

2. In :a cathode ray tube, an evacuated envelope having an electron permeable window, :a control grid close to the window, and other electrodes to contnol electrons entering through the window and passing through the control electrode and to accelerate the same, a target in the path of the electrons, a cooperating evacuated tube having an electnon permeable window positioned in electnon transfer relationship to the permeable window of the envelope, a cathode, an accelerating grid between the cathode and the second permeable window, and means detachably coupling the tube to the envelope.

3. In a cathode ray tube, an evacuated envelope having an electron permeable window, a control grid within the envelope in the path of movement of electrons entering the envelope through the window, beam forming, focusing and electron accelerating electnodes within the envelope, a target supported by the envelope against which the electnons impinge, a cooperating evacuated tube having an electron permeable window and means therein for generating .an electron beam and propelling the same through the window, and means detachably coupling the tube to the envelope with the windows in registration with each other and contacting.

4. In a cathode ray tube, an evacuated envelope having an electron permeable window lying a recess in the tube Wall, a control grid within the envelope in the path of movement of electrons entering the envelope through the window, beam forming, focusing and electron accelenating electrodes the envelope, a target supported by the envelope against which the electrons impinge, a cooperating evacuated tube having an electron permeable window and means therein for generating an electron beam and propelling the same through the window, and means detachably coupling the tube to the ergelope with the windows in registration with each o err.

5 6 5. In a cathode ray tube, an evacuated envelope having the envelope and tube, and a single socket detachably con- ,an electron permeable window, a oontrol grid Within the neoted to leads from the envelope and tube.

envelope in the path of movement of electrons entering the envelope Ough the Window, beam forming lfiocus References Cited 1n the file of thrs patent ing and electron accelerating electrodes within the en- 5 UNITED STATES PATENTS velope, a target supported by the envelope against which 2,536,27 5 (when Aug 10 v1954 the electrons impinge, a cooperating ewacnated tnbe hav- 2 7 97 Sessions May 1, 1956 ing an electron permeable window and means therein for generating an electron beam and propelling the same FOREIGN PATENTS through [the Window, leads connected with electrodes in 10 519,015 Great Britain Mar. 14, 1940 

1. IN A CATHODE RAY TUBE, AN EVACUATED ENVELOPE HAVING AN ELECTRON PERMEABLE WINDOW, A CONTROL GRID WITHIN THE ENVELOPE IN THE PATH OF MOVEMENT OF ELECTRONS ENTERING THE ENVELOPE THROUGH THE WINDOW, BEAM FORMING, FOCUSING AND ELECTRON ACCELERATING ELECTRODES WITHIN THE ENVELOPE, A TARGET SUPPORTED BY THE ENVELOPE AGAINST WHICH THE ELECTRONS IMPINGE, A COOPERATING EVACUATED TUBE HAVING AN ELECTRON PERMEABLE WINDOW AND MEANS THEREIN FOR GENERATING AN ELECTRON BEAM AND PROPELLING THE SAME THROUGH THE WINDOW, AND MEANS DETACHABLY COUPLING THE TUBE TO THE ENVELOPE WITH THE WINDOWS IN REGISTRATION WITH EACH OTHER. 